I'm not sure you understand what agnostic means. Everyone is agnostic. Agnosticism addresses the question of whether or not it is possible and/or important to know that a god exists. Being that no one truly possesses knowledge toward answering this question, one has no choice other than to be an agnostic. Claiming otherwise is intellectually dishonest.

"Spiritual" is a very slippery term that means whatever someone using it says it means. Nothing more nor less. So when people identify as "spiritual" they are potentially talking right past what your concept of the word is.

There's even a (reasonably good) book by Andre Compte-Sponville titled "The Little Book of Atheist Spirituality". It's not REALLY about what most people think of as spirituality, it is about the pursuit of the so-called Great Virtues. The book is meant to show that virtue, integrity, ethics, and morality are not outside the provenance of unbelievers, quite the opposite. It shows a rational basis for transcending the human condition.

When someone claims to be spiritual as an unbeliever or doubter it is really saying "I'm not abandoning my empathy, compassion, ethics or pursuit of meaning and purpose just because I'm distancing myself from the place most people profess to get those things from". Or at least that's the way I generally take it.

Also a minority of atheists pursue actual religion. Typically they either are covert atheists, usually in a theologically liberal church; or they are open atheists in an atheistic religion like Unitarian-Universalism or Buddhism. The motivation is generally to get the things from religion that it's actually fairly good at providing (sometimes): community / belonging / refuge.

I am not religious, or spiritual. But I do revere the earth and am in awe of the universe. Some call that spiritual, I don't. I also say I consider the earth sacred and the universe divine, it makes me seem less like a robot.

Folks interpret the meaning of the word God differently. Those in in organised religions engage in worship in the hope that their God will improve their lives or the lives of others.

Then there are folks like me who use the word God as a shorthand for a beleif in there being a force beyond our competence to understand. However I don't worship "God", I don't expect it to control my life.

Not sure. I put "spiritual" because even though I no longer believe in the Bible or the Hebrew God, I still believe Einstein, that all matter is a form of energy and that it is all connected, so of course things happen that seem supernatural..but have nothing to do with "God," unless you agree with what Jesus allegedly said..that we are all gods.